1. Field of the Invention
The present invention relates to a turbine moving blade of a gas turbine suitably used in a power generation plant and so forth as well as a gas turbine comprising the moving blade, and more particularly, to a turbine moving blade provided with a cooling structure.
2. Description of the Related Art
It is effective to increase the temperature of the combustion gas (fluid) for operation at the turbine inlet in order to improve the thermal efficiency of industrial gas turbines used in power generation plants and so forth. On the other hand, since the heat resistance performance of the turbine moving blades, stationary blades and other members exposed to combustion gas is restricted by the physical properties of their materials, it is not possible to simply raise the turbine inlet temperature.
Therefore, thermal efficiency is increased by ensuring the heat resistance performance of the turbine blades by increasing the temperature of the turbine inlet while cooling the turbine blades with a cooling medium such as cooling air.
Examples of such turbine blade cooling methods include a convection cooling in which a cooling medium is made to flow within the turbine blades, and an impingement cooling. In addition, a film cooling is also used in which the cooling medium is blown onto the outer surface of the turbine blades to form a cooling medium film.
The following provides an explanation of the structure of a turbine moving blade of the prior art using FIGS. 7 and 8.
As shown in the internal cross-sectional view of FIG. 7, a turbine moving blade 50 has three internal flow paths 51, 52 and 53 through which a cooling medium flows, supply openings 51a, 52a and 53a through which a cooling medium is supplied are provided in the base end surfaces, and a plurality of blow-out openings are formed in the outer surface for blowing out a cooling medium. As shown in the cross-sectional view of FIG. 8, the blow-out openings comprise leading edge blow-out openings 54 provided in leading edge 64 of the turbine moving blade 50, blade surface blow-out openings 55 provided in the blade surface, and trailing edge blow-out openings 56 provided in the trailing edge 66. The trailing edge blow-out openings 56 are provided at a plurality of locations from the vicinity of the blade base 57 to the vicinity of the blade tip 58 along the trailing edge 66, and each the trailing edge blow-out opening 56 is formed to the same dimensions. Numerous blade surface blow-out openings 55 are provided in the high-pressure side blade surface 65, and are inclined either towards the direction of the leading edge or the direction of the trailing edge. Showerhead cooling is performed by blow-out A from the leading edge blow-out openings 54, total surface film cooling is performed by blow-out B from the blade surface blow-out openings 55, and slot cooling is performed by blow-out C from the trailing edge blow-out openings 56.
In addition, a plurality of turbulators 59 are provided so as to be inclined relative to the flow of the cooling medium for improving cooling efficiency by agitating the flow of the cooling medium. In the case of the internal flow path 52 having two U-turn sections, the turbulators 59 are provided as follows. That is, on the upstream side of the U-turn section 60, the turbulators are provided so as to be inclined upstream to downstream when facing from a wall that is continuous with the inside wall 61 of the U-turn section 60 towards a wall that is continuous with the outside wall 62 of the U-turn section 60. On the downstream side of the U-turn section 60, the turbulators 59 are inclined so as to have the opposite orientation. Since the orientation of the turn of the next U-turn section 63 is opposite of that of the turn of U-turn section 60, the inclination of turbulators 59 on the downstream side of the U-turn section 60 becomes the inclination of the turbulators 59 on the upstream side of the U-turn section 63.
However, in the turbine moving blade 50 as described above, although various contrivances are made to ensure heat resistance performance, in the case cooling is still not adequate, there was the problem of burning and chipping at various locations of the turbine moving blade 50 such as in the blade tips and the blade surfaces. For example, since the temperature of the cooling medium supplied from the supply openings 51a, 52a and 53a of the base end surface of the urbine moving blade 50 rises as it passes through the internal flow paths 51, 52 and 53 and approaches the blade tip, there was the problem of cooling effects decreasing at the blade tip. As a result, not only is the lifetime of the turbine moving blade 50 shortened and the operating efficiency of a gas turbine using this turbine blade 50 decreased, but there was also the problem of a decrease in thermal efficiency.